MgSO_4-冻融循环作用下风积沙混凝土的微观孔隙研究

Micropore of Aeolian Sand Concrete under MgSO_4-Freeze-Thaw Cycles

以风积沙等质量替代河砂,制备了不同风积沙替代率的混凝土,并探究了其在清水和质量分数为3%,6%的MgSO_4溶液中经历冻融循环后的损伤失效规律.借助核磁共振、场发射扫描电镜和能谱仪,分析了风积沙混凝土内部微观孔隙变化及水化产物.结果表明:在6%MgSO_4溶液中冻融循环对混凝土的损伤最小;随着风积沙替代率的增加,混凝土孔隙度降低,自由流体饱和度下降,抗渗性增强;MgSO_4与水化产物反应生成的钙矾石会填充试件孔隙,进一步抑制MgSO_4参与反应;风积沙混凝土具有合理的孔隙结构且渗透率较低,其在不同冻融介质中的抗冻耐久性明显提升.

The river sand was replaced by aeolian sand,and the concrete with different aeolian sand substitution rate was prepared.The damage failure law in mass fractions of 3%and 6%MgSO 4 solution and in clear water was investigated.With nuclear magnetic resonance(NMR),field emission scanning electron microscopy and energy dispersive spectrometer,the microscopic pore changes and hydration products in the aeolian sand concrete were analyzed.The results show that the freeze-thaw cycle has the least damage to concrete in 6%MgSO 4 solution;with the increase of aeolian sand replacement rate,the concrete porosity decreases,the free fluid saturation decreases,and the impermeability is enhanced.The ettringite formed by the reaction of MgSO 4 with the hydration product will fill the pores of the test piece and further inhibit the participation of MgSO 4.The aeolian sand concrete has reasonable pore structure and low permeability,and its anti-freeze durability in different freeze-thaw media is obviously improved.